Process for the separation of phenol from phenylphenols



Patented Nov. 17, 1942 UNHTED STATES ATENT OFFICE PROCESS FOR THE SEPARATION OF PHENOL FROM PHENYLPHENOLS N Drawing. Application June 6, 1938, Serial No. 212,125. In Germany June 18, 1937 1 Claim.

In the manufacture of phenol from halogenated benzol such as chlor benzol, by the action of sodium or other alkali compounds, there are ordinarily produced as byproducts ortho and para phenylphenols. These are present in the form of sodium compounds, and the sodium is later removed by the use of an acid. Due to the phenolic character of the phenylphenols it is difficult to separate phenol from the phenylphenols either before or after the acidification.

In previous practic the separation of the phenol and phenylphenols has been efiected in a still equipped with a suitable column, but this method of separation is difficult and inconvenient, and requires special apparatus, as the boiling point of the phenylphenols is in the vicinity of 300 C. At these higher temperatures it is diificult if not impossible to prevent the formation of reaction products such as tarry bodies, and therefore the yield is correspondingly reduced.

It has been discovered that the separation may be quantitatively effected Without the danger of formation of any tarry byproducts, and at comparatively small expense, and with very simple apparatus.

In carrying out the present process the separation is effected by taking advantage of the different acidic properties of the phenol and the phenylphenols. I have discovered that the phenylphenols are much weaker acids than the phenol itself. Therefore, by controlling and limiting the acidification of the alkaline solution of the phenols and phenylphenols, the phenylphenols may be freed from their corresponding sodium or other alkali metal compounds and separated from the solution before the acidification of the phenol. By determining the relative percentage of the sodium phenolate and sodium phenylphenolate in the alkaline solution, and adding only such an amount of acid as will acidify the phenylphenols, these may be separated quantitatively and thereafter, upon further acidification, the phenol may be obtained free from phenylphenols.

After the liberation of the phenylphenols they may be removed by extraction With a suitable solvent such as benzol or chlor benzol, which is not a solvent for the sodium phenolate, which has not been converted into phenol due to the fact that only sufiicient acid was added to effect the formation of the phenylphenols from the sodium phenylphenolate.

By means of my improved process yields of pure phenol with a solidifying point of 40 C. may be obtained. For the partial acidification and the separation of the phenylphenols I employ phenol, which is a weak organic acid and of a stronger acid character than phenylphenol. The phenol reacts with the sodium of the sodium phenylphenols to form further sodium phenolate and liberate the phenylphenols.

As an example, a solution containing sodium phenolate and sodium phenylphenolate, and produced by the high pressure saponification of chlor benzol with caustic soda solution, may contain sodium phenolate in an amount corresponding to grams of phenol and sodium phenylphenolates in an amount corresponding to 17 grams of ortho and para phenylphenol. This solution is partly precipitated with phenol. This amount of phenol will react with the sodium phenylphenolates to form more sodium phenolate and phenylphenols.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

The process of separating phenylphenols from an alkaline solution containing sodium phenolate and sodium phenylphenolate, which includes adding phenol to liberate the phenylphenols and form additional sodium phenolate.

KURT BUCHHEIM. 

